Capital-Skill Complimentarity: Evidence from Manufacturing Industries in Ghana

Using U.S. manufacturing data, Griliches (1969) found evidence suggesting that capital equipment was more substitutable for unskilled than skilled labor. Griliches formulated this finding as the capital-skill complementarity hypothesis. The purpose of this study is to determine whether the capital-skill complementarity framework holds for Ghana manufacturing plants in industry and aggregate level. We use an unbalanced panel of plant-level data for manufacturing firms in Ghana during the 1991 and 1997 in four industries (food-bakery, textiles-garments, wood-furniture and metal-machinery). Our findings suggest that capital-skill complimentarity holds in aggregate level and wood-furniture sector in Ghana. However, we reject the capital-skill complementarity hypothesis for food-bakery, textile-garment and metal-machinery sectors.capital-skill complementarity, elasticity of substitution, translog cost function

A Bioinspired Hierarchical Underwater Superoleophobic Surface with Reversible pH Response

The development of oil-repellent surfaces in liquid environments has received considerable attention because of the urgent demand for antifouling coatings in marine industry. Inspired by the unique nanostructure surface of filefish scale, hierarchical films that consist of poly(pentafluorophenyl acrylate) free standing micropillars grafted with pH responsive poly(methacrylic acid) nanobrushes are fabricated by anodic aluminum oxide templating method combined with a subsequent post-polymerization modification strategy. The obtained films exhibit constantly underwater superoleophobicity, furthermore, a pH sensitive functionality, which enables reversible switching between low and high oil adhesion as a result of the adjustable oil sliding angle. This particular study provides a very mild method for the facile fabrication of bioinspired nanostructures with excellent oil-repellent performance and switchable oil-adhesion properties, thus paving the way toward novel functional materials with smart structures for promising applications, such as smart microfluidics, controllable bioadhesion, and intelligent materials for oil removal treatment and marine antifouling

A CO2_{2}-gated anodic aluminum oxide based nanocomposite membrane for de-emulsification

A carbon-dioxide-responsive organic–inorganic nanocomposite membrane based on a through-hole anodic aluminum oxide (AAO) template was constructed. The composite was prepared via a surface-initiated reversible addition–fragmentation chain-transfer (SI-RAFT) polymerization strategy to achieve the grafting of poly(methyl methacrylate-co-2-(diethylamino)ethyl methacrylate) brushes on the AAO membrane. The grafted polymer chain length could be controlled based on the feed ratio between the free chain transfer agent (CTA) and reactive monomer, e.g., methyl methacrylate and 2-(diethylamino)ethyl methacrylate, resulting in a membrane that features adjustable water permeability. Importantly, the membrane pore size and surface wettability could be switched from hydrophobic to hydrophilic upon the introduction of carbon dioxide and nitrogen gases. This allowed for the nanocomposite membrane to be utilized for controlled water flux and oil/water emulsion separation. The simple fabrication methodology as well as sustainable gaseous stimulus will be useful for the construction of future smart membranes

Pressure-tuning of the c-f hybridization in Yb metal detected by infrared spectroscopy up to 18 GPa

It has been known that the elemental Yb, a divalent metal at mbient pressure, becomes a mixed-valent metal under external pressure, with its valence reaching ~2.6 at 30 GPa. In this work, infrared spectroscopy has been used to probe the evolution of microscopic electronic states associated with the valence crossover in Yb at external pressures up to 18 GPa. The measured infrared reflectivity spectrum R(w) of Yb has shown large variations with pressure. In particular, R(w) develops a deep minimum in the mid-infrared, which shifts to lower energy with increasing pressure. The dip is attributed to optical absorption due to a conduction c-f electron hybridization state, similarly to those previously observed for heavy fermion compounds. The red shift of the dip indicates that the $c$-$f$ hybridization decreases with pressure, which is consistent with the increase of valence.Comment: 2 pages, to appear in J. Phys. Soc. Jpn. Supp

Compact wavelength de-multiplexer design using slow light regime of photonic crystal waveguides

Cataloged from PDF version of article.We demonstrate the operation of a compact wavelength de-multiplexer using cascaded single-mode photonic crystal waveguides utilizing the slow light regime. By altering the dielectric filling factors of each waveguide segment, we numerically and experimentally show that different frequencies are separated at different locations along the waveguide. In other words, the beams of different wavelengths are spatially dropped along the transverse to the propagation direction. We numerically verified the spatial shifts of certain wavelengths by using the two-dimensional finite-difference time-domain method. The presented design can be extended to de-multiplex more wavelengths by concatenating additional photonic crystal waveguides with different filling factors. (C) 2011 Optical Society of Americ

Dual-frequency division de-multiplexer based on cascaded photonic crystal waveguides

Cataloged from PDF version of article.A dual-frequency division de-multiplexing mechanism is demonstrated using cascaded photonic crystal waveguides with unequal waveguide widths. The de-multiplexing mechanism is based on the frequency shift of the waveguide bands for the unequal widths of the photonic crystal waveguides. The modulation in the waveguide bands is used for providing frequency selectivity to the system. The slow light regime of the waveguide bands is utilized for extracting the desired frequency bands from a wider photonic crystal waveguide that has a relatively larger group velocity than the main waveguide for the de-multiplexed frequencies. In other words, the wider spatial distribution of the electric fields in the transverse direction of the waveguide for slow light modes is utilized in order to achieve the dropping of the modes to the output channels. The spectral and spatial de-multiplexing features are numerically verified. It can be stated that the presented mechanism can be used to de-multiplex more than two frequency intervals by cascading new photonic crystal waveguides with properly selected widths. (c) 2012 Elsevier B.V. All rights reserved

Risk factors for development of left ventricular thrombus after first acute anterior myocardial infarction-association with anticardiolipin antibodies

<p>Abstract</p> <p>Background</p> <p>Left ventricular thrombus(LVT] formation is a frequent complication in patients with acute anterior myocardial infarction(MI). LVT is associated with increased risk of embolism and higher mortality rates after acute MI. Anticardiolipin antibodies (ACA) are immunoglobulins that react with phospholipid-binding proteins interfering with the prothrombin activator complex. The effects of phospholipids on pathophysiology of cardiovascular thrombotic events are well known. In this study, we aimed to evaluate the importance of clinical and biochemical parameters including anticardiolipin antibodies on left ventricular thrombus formation after acute anterior MI.</p> <p>Methods and Results</p> <p>Seventy patients with a first anterior AMI were prospectively and consecutively enrolled. Patients with previous MI, autoimmune disease, collagen vascular disease and arterial or venous thrombosis history were excluded from this study. At the time of hospitalization, key demographic and clinical characteristics were collected including age, gender, ethanol intake and presence of traditional risk factors for atherosclerosis (hypertension, diabetes, smoking, hyperlipidemia, positive family history). Patients were evaluated for echocardiographic data, blood chemistry and ACA. Two-dimensional and Doppler echocardiographic examinations were performed in all patients within the first week and at 14 days after MI. LV thrombus was detected in 30 (42.8%) patients. ACA IgM levels were significantly higher in the patient group with LV thrombus than in the group without thrombus (12.44 ±4.12 vs. 7.69 ± 4.25 mpl, p = 0,01). ACA IgG levels were also found higher in the group with LV thrombus (24.2 ± 7.5 vs.17.98 ± 6.45 gpl, p = 0.02). Multivariate analyses revealed diabetes mellitus, higher WMSI, lower MDT and higher ACA IgM and higher ACA IgG levels as independent predictors of left ventricular thrombus formation.</p> <p>Conclusions</p> <p>Our data demonstrate that beside the low ejection fraction, lower MDT and higher wall motion score index, modestly elevated ACA IgM and ACA IgG levels are associated with LV thrombus formation in patients with anterior MI.</p